1. Field of the Invention
The present invention relates to a toner that is used, for example, in electrophotographic methods, electrostatic recording methods, and toner jet methods.
2. Description of the Related Art
There has been increasing desire in recent years for less expensive and smaller copiers and printers.
Corresponding to this demand, toners are being required that provide a desirable image density at smaller amounts and that can generate a high image quality even during long-term use and use in a high-temperature, high-humidity environment or a low-temperature, low-humidity environment.
In response to these requirements, a method exists that provides a toner that even in small amounts exhibits a high tinting strength; this is achieved by using a pigment dispersing agent that has at least one aromatic skeleton as well as a base skeleton that is compatible with the binder resin, thereby maintaining pigment dispersity by π-π interactions by the π-electrons of the aromatic ring in the pigment dispersing agent (for example, Japanese Patent laid-open No. 2010-152208).
However, some problems are still present in terms of the offset resistance and fogging in a high-temperature, high-humidity environment or a low-temperature, low-humidity environment.
Moreover, a method exists that provides a toner in which the offset resistance coexists in balance with a high image quality; this is achieved by specifying certain prescribed ranges for the SP values of the binder resin and a resin used for pigment dispersion, thereby maintaining a uniform dispersion of the pigment and suppressing a highly disperse state by a polyolefin wax in the binder resin (for example, Japanese Patent laid-open No. H07-219274).
However, the tinting strength of the toner is not adequate due to an inadequate state of dispersion by the pigment in the toner and some problems are also still present with respect to fogging in a high-temperature, high-humidity environment or a low-temperature, low-humidity environment.
In addition to the preceding, various pigment dispersing agents have been proposed in order to improve the dispersion of the pigment in the toner. For example, a toner has been disclosed that contains a binder resin, carbon black, and a graft copolymer or block copolymer comprising a styrene-type polymer and an acrylate ester-type polymer or a methacrylate ester-type polymer (for example, Japanese Patent Publication No. 3,285,623).
A method has also been disclosed for producing a toner particle that contains an amide group-bearing compound and a zinc phthalocyanine compound (for example, Japanese Patent Publication No. 4,510,687).
However, in both instances some problems still remain with respect to the charging performance in particular in a high-temperature, high-humidity environment.